Field of the Invention
The present invention relates to a sealing device sealing an outer periphery of a rotating body in a motor vehicle, a general machine, an industrial machine and the like by a seal lip, and particularly relates to a sealing device in which a screw protrusion for obtaining a sealing performance on the basis of a screw pump action is formed in a seal lip.
Description of the Conventional Art
FIG. 5 shows an example of a sealing device according to a prior art in which a screw protrusion for obtaining a sealing performance on the basis of a screw pump action is formed in a seal lip. The sealing device 100 is provided with a seal lip 110 which is integrally formed by a rubber-like elastic material (a rubber material or a synthetic resin material having a rubber-like elasticity) in a reinforcing ring 120 made of a metal, and is structured such that a sealing space side conical surface 112 and an opposite sealing space side conical surface 113 are formed in an inner peripheral surface of the seal lip 110 while setting a lip edge 111 having the smallest diameter, the sealing space side conical surface 112 being larger in diameter toward a sealing space (a machine inside) A side and the opposite sealing space side conical surface 113 being larger in diameter toward an opposite sealing space side (an opposite side to the sealing space A). Further, a lot of screw protrusions 114 extending at a predetermined angle of incline in relation to a circumferential direction are formed in the opposite sealing space side conical surface 113. Each of the screw protrusions 114 is formed into a bilge shape in which a height and a width change little by little so that the height and the width are the maximum in an intermediate portion in a longitudinal direction, and a leading end thereof extends to the lip edge 111. Further, a garter spring 130 for compensating a tension force is installed to an outer peripheral portion of the seal lip 110.
The sealing device 100 is structured such as to inhibit the oil to be sealed in the sealing space A from leaking from a shaft periphery to an external space (the opposite sealing space) B side since a whole periphery of the lip edge 111 in the seal lip 110 is slidably brought into close contact with an outer peripheral surface of a rotating shaft 200. Particularly, since the screw protrusions 114, 114, . . . bring about the screw pump action together with the rotation of the rotating shaft 200 in a direction R, that is, an action of pushing the oil to be sealed which is going to leak around the shaft periphery to the external space B side, back to the sealing space A side, an excellent sealing performance is achieved (refer, for example, to Japanese Patent No. 3278349).